Double acting gas multi cylinder external combustion engine

ABSTRACT

To provide an engine construction in which both the hot gas connections and the cold gas connections will not differ in length and will be short, the operating piston-cylinder units are aligned in a row and the regenerator-cooler units are disposed in two rows flanking the cylinder rows. The heater tubes forming part of the hot gas connections form one or more walls of tubes disposed above the cylinders, and a combustion chamber can be arranged to apply heat to these tubes in the upper part of the engine. Engines of various sizes may be built out of identical units comprising a cylinder, a regenerator cooler and a hot gas connection.

United States Patent [191 Reuchlein June 28,1974

[ DOUBLE-ACTING GAS MULTI-CYLINDER EXTERNAL COMBUSTION ENGINE [75Inventor: Giinter Reuchlein, Gersthofen,

Germany 22 Filed: June 13, 1973 [21] Appl. No.: 369,704

[30] Foreign Application Priority Data June 27, 1972 Germany 2231360[52] US. Cl. 60/525 [51] int. Cl. F03g 7/06 [58] Field of Search 60/517,518, 524, 525, 60/526 [56] References Cited UNITED STATES PATENTS2,616,249 11/1952 DeBrey ..60/526 2,909,902 10/1959 Newton 50/526 X3,011,306 12/1961 Meyer....

3,180,078 4/1965 Liston....

3,527,049 9/1970 Bush 60/524 X Primary Examiner-Edgar W. GeogheganAssistant Examiner-H. Burks Attorney, Agent, or Firm-Flynn & Frishauf[571 ABSTRACT To provide an engine construction in which both the hotgas connections and the cold gas connections will not differ in lengthand will be short, the operating piston-cylinder units are aligned in arow and the regenerator-cooler units are disposed in two rows flankingthe cylinder rows. The heater tubes forming part of the hot gasconnections form one or more walls of tubes disposed above thecylinders, and a combustion chamber can be arranged to applyheat tothese tubes in the upper part of the engine. Engines of various sizesmay be built out of identical units comprising a cylinder, a regeneratorcooler and a hot gas connection 20 Claims, 6 Drawing Figures SHEEY '0[IF 6 PAIENIEUmza m4 DOUBLE-ACTING GAS MULTl-CYLINDER EXTERNALCOMBUSTION ENGINE Cross reference to related applications: U.S. Ser. No.346,107 filed Mar. 29, 1973. Cross reference to related applications:U.S. Ser. No. 315,930 filed Dec. 18, 1972.

U.S. Ser. No. 317,778 filed Dec. 22, 1972.

This invention concerns a double-acting multicylinder gas engine of theexternal combustion type in which the cylinders are in line and each isconnected over a hot gas connection to a regenerator which in turn isconnected, through a cooler and a cold gas connection, to the cold spaceof another cylinder which is either the adjacent cylinder or one nextbeyond the adjacent cylinder.

Double-acting thermal gas piston engines of the external combustion typeare known from German patent 802,486 and the corresponding US. Pat. No.2,611,235, so that the general construction and the principle ofoperation of such engines is known. Little is known, however, regardingfavorable arrangements of the heater, regenerator and cooler of such anengine. The question of the disposition and length of the gasconnections in the hot and cold regions and between connected cylindersare extremely important for the efficiency and safety of the entireengine.

It is an object of this invention to provide an arrangement of the gasconnections and of the heater, regenerator and cooler, in relation tothe cylinders of an external combustion engine which is highlyefficient, compact, economical and safe. In particular it is an objectof the invention to provide such an engine with short cold gasconnections of approximately equal length and likewise short hot gasconnections of approximately equal lengths.

SUBJECT MATTER or THE PRESENT INVENTION Briefly, each regenerator ishoused with a cooler in a common casing and these casings are disposedin two rows which flank the single row of cylinders on both sides. Thetwo rows of these casings each contain the same number of casings andthey may be relatively staggered longitudinally, although in any casethese two rows overlap in large part. These casings and their containedunits form part of interconnecting means, including a hot gas connectionand a cold gas connection, which interconnect the hot working space ofone cylinder with the cold working space of another cylinder, which iseither the next cylinder, when the last mentioned cylinder is at the endof the cylinder row, or the after-next cylinder in all other cases. Inevery case the combination of cylinder, hot gas connection andregenerator-cooling casing has the same configuration. Only in the coldgas connection is there a difference in the configuration for theconnection at the end of the cylinder row and the connections within thecylinder row, and even that difference is very small and does notinvolve a substantial difference in the length of the connection. Inconsequence, engines with different numbers of cylinders in the cylinderrow can all be built with identical cylinder-heater-regenerator-coolermodules, while maintaining in each case equality of the gas connectionlengths, thus keeping to a minimum the socalled dead space and greatlyreducing the energy losses related to gas flow.

LII

The two rows of regenerator casings flanking the row of cylinders arepreferably parallel and of the same length and may be opposite eachother or staggered, in the latter case by not more than one cylinderunit space. The hot gas connections are provided with arrays of heatertubes interposed between suitable manifolds. The heater tubes are intwo-leg form with one leg either returning parallel to the other ordisposed at a diverging angle. The tubes are arranged in parallel arraysforming one or more walls of parallel tubes which may be disposed aroundor across a common combustion chamber located above the cylinders,regenerators, etc. In this combustion chamber, one or more burners mayact on the heater tubes. One burner may apply heat to more than oneheater tube array or even to the arrays of heater tubes of more than onehot gas connection, so that the choice of the number of burners isindependent of the number of heater tubes or of unit heater tube arrays.

In a particularly useful arrangement, the axis of the cylinder and thatof the regenerator casing connected to it by the hot gas connection areparallel to each other, and in the assembled engine the respectiveplanes so defined by the cylinder and regenerator casing axes of eachmodule are parallel to each other and are all oblique to the planecontaining the axes of all the cylinders.

It is advantageous to associate alternate members of the cylinder rowwith different regenerator casing rows, which is to say that if thecylinders are sequentially numbered in line, it is desirable to connectthe even numbered cylinders by hot gas connections to the regeneratorson one side of the cylinder row and to connect the odd numberedcylinders by hot gas connections to the regenerators on the other side.By this alternating arrangement of the regenerator casings room isprovided for heater means of extended dimensions composed of long arraysof many heater tubes, disposed so as to form continuous heater tubewalls above each of the regenerator casing rows. In this embodiment ofthe invention, it is feasible to provide relatively short heater tubesthat are easily made by casting. This configuration has the furtheradvantage of reducing the height of the engine and providing a desirablelow profile.

The invention will be described by way of example with reference to theaccompanying drawings, wherein:

FIG. 1 is a plan view diagram of an embodiment of the invention;

FIG. 2 is a perspective view of the embodiment shown in FIG. 1;

FIG. 3 is a cross-sectional view of the embodiment shows in FIGS. 1 and2;

FIG. 4 is a cross-sectional view of another embodiment of the inventioncorresponding to FIG. 1;

FIG. 5 is a diagrammatic plan of another embodiment of the invention,and

FIG. 6 is a cross-section of the embodiment shown in FIG. 5.

The in-line motor shown in FIG. I has six cylinders, l-6, arranged in astraight row. Each cylinder contains a hot and a cold working space. Thehot space of a first cylinder is connected for cooperation with the coldspace of another cylinder, and so on, to provide the necessary enginework cycle. The flow path between a hot and a cold working space for theworking medium that flows back and-forth is completed by hot gasconduits connected to the hot work space and cold gas conduits connectedto the cold work space.

In the example shown in FIG. 1, the hot conduits 7 are each showndiagrammatically by lines enclosing a space. The cold conduits 8 arediagrammatically shown with dot-dash lines. Each hot conduit 7 connectsthe hot space of a cylinder with a regenerator that is housed in acommon casing with a cooler with which it connects. The cooler isconnected by a cold conduit 8 with the cold working space of anothercylinder.

The casings each containing a regenerator and a cooler are designatedwith reference numerals 9 to 14. These casings are arranged in twoparallel rows, one on each side of the cylinder row. The casings 9, 11and 13 are connected by hot conduits 7 with the odd numbered cylindersand the casings 10, 12 and 14 of the other row are similarly connectedto the even numbered cylinders. Each of the casings 9-14 stands oppositeto a cylinder which is next to the cylinder with which the casing isconnected by the hot conduit 7. Thus, the casing 9 associated with thecylinder 1 is disposed laterally opposite cylinder 2, and the casing 14associated with cylinder 6 stands laterally next to cylinder 5. Theoffsetting of the casings with respect to the associated cylinders thuscorresponds to one cylinder unit space. The casings of one casing roware offset in the same direction with respect to the cylinders to whichthey are connected by a hot conduit, and the offsets of the two rows arein opposite directions. In consequence, the two rows of casings arestaggered by one cylinder unit space, so that each casing of a casingrow stands opposite the gap between two casings in the other casing row.

In this arrangement each combination of cylinder, hot conduit and casinghas the same configuration, so that component parts of the sameconfiguration may be used for all of. these modules. In the arrangementof FIG. 1, these modules are used in interlocking orientations. Eachmodule can accordingly be preassembled and individually stored, so thatas needed they may be combined quickly and simply for the assembly ofmotors of different numbers of cylinders.

The two end cylinders l and 6 are provided with cold conduits 8 runningperpendicularly to the longitudinal axis of the cylinder row to connectrespectively with casings and 13 which are located laterally oppositethe end cylinders. The other cold conduits 8 providing the connectionsbetween the aforementioned modules are all parallel, but are oblique,being somewhat off the perpendicular, with respect to the longitudinalaxis of the engine. It is simple to choose the lengths of the coldconduits so that those connected to the end cylinders are of the samelengths as those connected to the other cylinders, and so that all thecold conduits have the same lengths. Since only neighboring modules areconnected by the cold conduits, both in the middle and at the ends ofthe row, and since the modules are simply offset or turned around withrespect to each other, it is possible to use very short cold conduits 8.As the result of the small volume of the flow paths thus obtained in theindividual work cycle combinations interconnecting the cold space of onecylinder with the hot space of another, it is possible in this way toreduce greatly the so-called dead spaces and to obtain an increase ofthe overall efficiency of the machine. A reduced quantity of the flowmedium, moreover, will then suffice to fill all the individual workcycle units of the machine completely. This arrangement, finally, hasthe further advantage of providing non-interfering paths for the coldconduits. It is not necessary to distort the paths of these conduits topass them around each other. This means also that the engine is easy toassemble in a gas-tight fashion, because of the substantially straightand short cold conduits that make the operative connections between themodules. The equality in the lengths of the cold gas connections notonly makes possible economies in the production of these components, butsimplifies the assembly, just as the identical configuration of eachmodule and of its component part produces economies in parts cost and inassembly work. The number of casting patterns involved, for example, isgreatly reduced. Storage space requirements for parts is reduced becauseof the smaller number of different parts involved.

Because all the operative parts of a thermal gas engine must be solderedor screwed together in gas-tight fashion, a readily grasped functionalpattern and good accessibility for assembly is unusually important.Furthermore, it is possible with this sort of a piping plan, where thereare no cross-overs of the cold conduits, to provide manifolds at thecold side of the casing containing a cooler and a regenerator, betweenthe cooler and the cold conduit, so as to obtain favorable flowcharacteristics in the neighborhood of the cold conduits. Then, becauseall of the coldconduits have the same length, the distribution of theload among cylinders does not get out of balance, a factor whichcontributes to the increased efficiency of the whole machine.

The principle of operation of a double-action thermal gas piston engine,as already mentioned, is described in U.S. Pat. No. 2,611,235. Theconstruction of the pistons and cylinders, as well as connectionsthrough the crankshaft is shown in copending patent application U.S.Ser. No. 315,930, filed Dec. 18, 1972, the disclosure there, however,being a V engine rather than an in-line engine. Briefly stated, themedium is heated and caused to expand while most of it is on the warmside of the regenerator and it is then caused to flow through theregenerator which stores a large part of the heat and then through thecooler, after which, when most of the medium is on the cold side of theregenerator, its pressure falls, so that it causes the piston on thecold side to reduce the cold working space, this providing thedouble-action, for at the same time hot gas is expanding on the otherside of that piston. In order that there may be expansion andcontraction of the medium in such a system without the provision ofauxiliary pistons, the gas on the cold side of the regenerator duringthe time most of the gas handled by that regenerator is on the hot sideof it is working with a piston moving slowly near its dead spot, whilethe larger portion of gas is hot and expanding against a piston near themiddle of its stroke. The converse holds when most of the gas is on thecold side. The amount of relative displacement of the piston cycles ofthe various cylinders is one of the elements of the design of theengine. In the example shown in FIG. 2, as may be seen from thecrankshaft 17, the six cylinders have their strokes evenly staggered inflow connection sequence so as to provide substantially uniformtransmission of power to the crankshaft.

The form of the hot conduits 7 can be particularly well seen in FIG. 2.Each cylinder has a piston which is connected with a diagrammaticallyshown crankshaft 17 by means of a likewise schematically drawn pistonrod 16. In this case the hot working space 18 is above the piston 15,while the cold working space 19 is below the piston. The operatingmedium, a gas chosen for its heat transfer and other physicalcharacteristics, flows from the hot working space 18 of a firstcylinder, for example cylinder 6, over the hot conduits 7, whichcomprises the manifolds 20 and 21 as well as the heater tubes 22,through a regenerator and a cooler, which in this case are in the casing14, then over the cold conduits 8 to the cold working space 19 of afurther cylinder, in this case the cylinder 4. The hot working spaces 18of the cylinders 1 to 6, all communicate with their respective manifolds20 which extend horizontally towards the appropriate one of the casings9 to 14. In the neighborhood of this regenerator casing, the wide end ofthe manifold 20 meets the wide end of a manifold 21 rising in a verticalplane. The manifold 20 is turned up at its wide end, so that the wideends of the manifolds 20 and 21 are adjacent side by side over a longlength. Here these manifolds are connected with an array of heater tubes22 that are bent in U-shape with two relatively long legs, so that thepassage through all these heater tubes connects the two manifolds andpermits the gas to flow from one to the other therethrough. The heatertubes 22 in a connection between a particular cylinder, for examplecylinder 6, with an associated regenerator and cooler contained in acommon casing, for example the casing 14, forms a heater unit 23.

As the result of the projecting and fanned out shape of the manifolds 20and 21, and by the provision of the heater tubes 22 as an array ofidentical components, the resultis obtained that'all of the branchstreams flowing through the respective heater tubes have approximatelythe same total flow path length. That has the advantage of avoidinglocal overloading of the heater 23, that is, thermal overloading ofparticular heater tubes 22, so that the operating temperature of theheaters can be brought close to the upper limit set by thecharacteristics of the material of which the heater tubes are made.

The several heaters 23 associated with the respective regeneratorcasings 9 to 14, above which they are located, form two continuousheater tube walls 24 and 25, which run parallel to each other over thefull length of the engine. The space above the cylinders 1 to 6 includedbetween the two heater tube walls 24 and 25 and provides a convenientplace, as further described below, for the location of a longitudinallyextending combustion chamber from which heat can be applied to bothheater tube walls.

FIG. 3 shows how acombustion chamber 26 can be provided between the twoheater tube walls 24 and 25. The combustion chamber 26 is fired by aburner system 27, which projects a flame from above down into thecombustion chamber 26. A heat shield 28 is located on top of thecylinder array, as a fire wall separating the engine from the combustionchamber 26, so as to avoid overheating of the components located belowthe combustion chamber. As already mentioned above, the combustionchamber 26 extends longitudinally over the whole length of the engine.The number of the burners forming the burner system 27 can accordinglybe independent of the number of the heaters 23 and can be determinedsimply with reference to burner efficiency. In a particularly simpleembodiment, a single burner can be quite sufficient to provide thenecessary heat for the engine.

The combustion product gases issuing from the combustion chamber 26,having already given up a major portion of the heat to the heater 23,flow through a preheater 29 located above the two heater tube walls 24and 25, where the combustion products give up a further portion of theirheat to the supply of combustionsupporting air which flowscountercurrent through the preheater 29 on its way to the burner system27. The

combustion products then issue to the atmosphere.

upon discharge from the preheater 29. An advantage of externalcombustion engines such as the present embodiment is that the combustioncan be completely carried out in the engine, so that the gases issuingto the atmosphere will be substantially free of noxious components. Thepath of the exhaust gases through the preheater is shown in FIG. 3 by acontinuous arrow, while that of the fresh air needed for combustion isshown by a dashed arrow. Asa rule the fresh air is supplied to thecombustion system 27 by a blower, not shown in this drawing.

In the embodiment of the invention shown in FIG. 4, the heater tubewalls 24 and 25 are formed of heater tubes 30 spread out in V-shape. Inthis case the hot gases have their direction of flow more graduallychanged in the neighborhood of the heater tube walls 24 and 25, so thatfavorable flow characteristics are obtained. The manifolds 20 and 21 inthis case are disposed in the same direction as the legs of the V-shapedheater tubes to which they are connected, so that energy losses as theresult of sharp changes of direction of the gas flow are also minimizedfor the flow of the working medium through the heater tubes 30.Furthermore, in the design of FIG. 4 the bending moment of the heatertubes, as the result of the difference in expansion of the leg facingthe flames compared to the leg away from the flames, is substantiallyreduced. Instead of the downwardly directed burner system 27, therecould be located directly above the cylinder array a burner system wherecombustion starts from below and extends upwardly. In such a case theheater tube walls 24 and.25 could then be inclined inwardly to form asort of roof over the burner, incidentally reducing the height of themachine as a whole.

FIG. 5 shows another embodiment of the invention in which the row formedby the casings 9, 11 and 13 and the row formed by the casings 10, 12 and14 are not relatively offset in their positions on the two sides of thecylinder row 1-6. The casings 9 and 10 respectively associated with thecylinders 1 and 2 are located opposite each other in the region of thegap between the cylinders 1 and 2. The casings 11 and 12 are similarlylocated in the neighborhood of the gap between cylinders 3 and 4, andcasings 13 and 14 likewise by the gap between cylinders 5 and 6. The hotconduits 7 again lead from the hot, working space of a cylinder, throughthe casing of the same module which contains a regenerator and a cooler,from which the cold conduits 8 leads to the cold working space ofanother cylinder. The connection plan of the casings of the two flankingcasing rows to the particular cylinders is the same as in the previouslymentioned example shown in FIG. 1: thus the odd numbered cylinders 1, 3and 5 are connected by hot conduits 7 to the casings 9, 11 and 13 of onecasing row and the even numbered cylinders 2, 4 and 6 are connected byhot conduits to the casings 10, 12 and 14 of the other casing row. Inthis case as well as in the case of FIG. 1, it is clear that thedisposition of the hot conduits 7 and that of the cold conduits 8 couldbe interchanged, provided attention is paid to the fact that there isnot more than one cylinder between two cylinders connected with casingsof the same row and that the end cylinders of the cylinder row areconnected by an applied conduit and through a regenerator to the nextcylinder in the row. The direction of rotation of the crankshaft wouldthen be simply reversed in this case. In the arrangement of FIG. the

heaters 31 associated with the hot conduits 7 are cated above thecylinder row and form continuous heater tube wall 32 extending over thelength of the engme.

As shown in more detail in FIG. 6, the heater tube wall 32 formed of theheaters 31 can with advantage be made inclined to one side, although ofcourse a vertical disposition of the heater tube wall is alsoconceivable. In the inclined arrangement shown in FIG. 6 a space savingcan be obtained by allowing the external combustion system 33 to projectto one side, so that it discharges the hot gases perpendicularly to theplane of the heatertube wall 32. In this way the hot gases coming out ofthe combustion chamber 34 flow straight through the heater tube wall 32without any previous change of direction. In this version of the engineof this invention, a preheater 35 is also used in which the fresh airneeded to support combustion is preheated. The preheater 35 is providedat the side of the engine in this case. Of course in this case also thecombustion chamber 34 and the preheater 35 can be made to occupy spacesextending along the full length of the engine.

The advantage of the embodiment just described is particularly that onlyone heater tube wall is provided, saving the expense for an additionalheater tube wall. In this case, however, longer heater tubes must beprovided in order to supply sufficiently large heat transfer surfaces.In the example shown in FIGS. l4, in which two heater tube walls areprovided in each case, the heater tubes can, on the other hand, be maderelatively short, which is a favorable factor for the overall shape ofthe machine, since it reduces the necessary height. The thermal gasmotors above described in each case have six cylinders. Obviously, theinvention here described can also be used in thermal gas engines withdifferent numbers of cylinders, for example 4 or 8. In the particularcase of an odd number of cylinders, all but one of theregenerator-cooler casings can be disposed in two rows flanking thecylinders and the odd one can be aligned with the cylinder row beyondone end of the cylinder array. This is an alternative for having therows of casings of different lengths when there is an odd number ofcylinders.

I claim: l. A double-acting thermal gas piston engine having a pluralityof cylinders successively adjacent in a straight row, each cylinderhaving a hot working space and a cold working space, comprising:

interconnecting means between the hot working space of each cylinder andthe cold working space of another cylinder, said means including a hotconduit connected to said hot working space, a cold conduit connected tosaid cold working space and a regenerator and a cooler interposed inseries between said hot conduit and said cold conduit in such a way thatsaid regenerator is connected to said hot conduit and said cooler .isconnected to said cold conduit, said regenerator and said cooler of eachinterconnecting means being contained in a common casing(9,l0,l1,12,l3,14);

said interconnecting means being so disposed that said row of cylinders(1,2,3,4,5,6), at least in the longitudinal direction, is flanked by twoat least partly overlapping rows (9,11,13 and 10,12,14) of said casings,that the end cylinders (1,6) of said row are connected to the endcasings (9,10 and 13,14) of said two rows of casings, and that the innercylinders (2,3,4,5) of said row are connected to two adjacent casings ofthe same casing row.

2. A double-acting thermal gas piston engine as defined in claim 1, inwhich said rows of casings (9,11,13 and 10,12,14) are disposed parallelto each other, are of the same length and are offset with respect toeach other by not more than one cylinder space of said cylinder row.

3. A double-acting thermal gas piston engine as defined in claim 1, inwhich said hot conduits (7) include parallel arrayslof two-leg heatertubes arranged so that said heater tubes of all said hot conduits (7)form at least one continuous heater tube wall (24,25,32).

4. A double-acting thermal gas piston engine as defined in claim 1, inwhich the central longitudinal axis of each cylinder (1 to 6) and thatof the casing'(9 to 14) connected to such cylinder over one of said hotconduits (7) lie in.a plane and in which, further, the said planes ofall said cylinder-casing pairs are parallel to each other and oblique tothe common plane of said central axes of said cylinders.

5. A double-acting thermal gas piston engine as defined in claim 1, inwhich said cold conduits (8) which are connected to those cylinders(2,3,4,5) which are interior members of said row of cylinders aredisposed parallel to each other.

6. A double-acting thermal gas piston engine as defined in claim 5, inwhich said cold conduits (8) which are connected to the two endcylinders (1,6) of said row of cylinders are disposed parallel to eachother.

7. A double-acting thermal gas piston engine as defined inclaim 6, inwhich all of said cold conduits (8) are of the same length.

8. A double-acting thermal gas piston engine as defined in claim 1, inwhich if the cylinders of said cylinder row are numbered in sequencebeginning with l, the even numbered cylinders (2,4,6) are connected withthe casings (9,11,13). of one casing row and the odd numbered cylinders(1,3,5) are connected with the casings (10,12,14) of the other casingrow.

9. A doubleacting thermal gas piston engine as defined in claim 3, inwhich each casing row (9,11,13 and 10,12,14) is connected to a separateheater tube wall (24,25).

10. A double-acting thermal gas piston engine as defined in claim 9, inwhich a combustion chamber (26) is provided between said two heater tubewalls (24,25).

11. A double-acting thermal gas piston engine is defined in claim 3, inwhich at least one leg of said heater tubes forming said heater tubewalls (24,25) is directed obliquely to the common plane of said centralaxes of said cylinders (1 to 6).

12. A double-acting thermal gas piston engine as defined in claim 2, inwhich the said casings (9 to 14), each containing a regenerator and acooler, are disposed so that said casings of each row are opposite everysecond interval between two cylinders.

13. A double-acting thermal gas piston engine as defined in claim 12, inwhich the heater tubes (32) are arranged in a heater tube wall disposedabove said cylinder row in a laterally offset combustion chamber (34).

14. A double-acting thermal gas piston engine as defined in claim 13, inwhich the plane of said heater tube wall (32) is disposed obliquely withrespect to the common plane of said central axes of said cylinders (1 to10 an elongated heat exchanger extending over substantially the fulllength of the engine.

17. A double-acting thermal gas piston'engine as defined in claim 15, inwhich a reinforced shield (28) is provided on the floor of saidcombustion chamber 26) for reversing the direction of flow of combustiongases.

18. A double-acting thermal gas piston engine as defined in claim 3, inwhich said heater tubes (22) are connected by manifolds (20,21)respectively with said hot working space and with said regenerator ofeach connecting means, and in which said manifolds provide a gradualchange in cross section.

19. A double-acting thermal gas piston engine as defined in claim 18, inwhich said manifolds extend in offset fashion from the respectivecylinders and casings and that the corresponding manifolds mutuallyoverlap in the region of the heater tube ends.

20. A double-acting thermal gas piston engine as defined in claim 19, inwhich the two manifolds (20,21) of the same interconnecting means havesubstantially the same cross section in the neighborhood of the ends ofthe heater tubes (22).

1. A double-acting thermal gas piston engine having a plurality ofcylinders successively adjacent in a straight row, each cylinder havinga hot working space and a cold working space, comprising:interconnecting means between the hot working space of each cylinder andthe cold working space of another cylinder, said means including a hotconduit connected to said hot working space, a cold conduit connected tosaid cold working space and a regenerator and a cooler interposed inseries between said hot conduit and said cold conduit in such a way thatsaid regenerator is connected to said hot conduit and said cooler isconnected to said cold conduit, said regenerator and said cooler of eachinterconnecting means being contained in a common casing(9,10,11,12,13,14); said interconnecting means being so disposed thatsaid row of cylinders (1,2,3,4,5,6), at least in the longitudinaldirection, is flanked by two at least partly overlapping rows (9,11,13and 10,12,14) of said casings, that the end cylinders (1,6) of said roware connected to the end casings (9,10 and 13,14) of said two rows ofcasings, and that the inner cylinders (2,3,4,5) of said row areconnected to two adjacent casings of the same casing row.
 2. Adouble-acting thermal gas piston engine as defined in claim 1, in whichsaid rows of casings (9,11,13 and 10,12,14) are disposed parallel toeach other, are of the same length and are offset with respect to eachother by not more than one cylinder space of said cylinder row.
 3. Adouble-acting thermal gas piston engine as defined in claim 1, in whichsaid hot conduits (7) include parallel arrays of two-leg heater tubesarranged so that said heater tubes of all said hot conduits (7) form atleast one continuous heater tube wall (24,25,32).
 4. A double-actingthermal gas piston engine as defined in claim 1, in which the centrallongitudinal axis of each cylinder (1 to 6) and that of the casing (9 to14) connected to such cylinder over one of said hot conduits (7) lie ina plane and in which, further, the said planes of all saidcylinder-casing pairs are parallel to each other and oblique to thecommon plane of said central axes of said cylinders.
 5. A double-actingthermal gas piston engine as defined in claim 1, in which said coldconduits (8) which are connected to those cylinders (2,3,4,5) which areinterior members of said row of cylinders are disposed parallel to eachother.
 6. A double-acting thermal gas piston engine as defined in claim5, in which said cold conduits (8) which are connected to the two endcylinders (1,6) of said row of cylinders are disposed parallel to eachother.
 7. A double-acting thermal gas piston engine as defined in claim6, in which all of said cold conduits (8) are of the same length.
 8. Adouble-acting thermal gas piston engine as defined in claim 1, in whichif the cylinders of said cylinder row are numbered in sequence beginningwith 1, the even numbered cylinders (2,4,6) are connected with thecasings (9,11,13) of one casing row and the odd numbered cylinders(1,3,5) are connected with the casings (10,12,14) of the other casingroW.
 9. A double-acting thermal gas piston engine as defined in claim 3,in which each casing row (9,11,13 and 10,12,14) is connected to aseparate heater tube wall (24,25).
 10. A double-acting thermal gaspiston engine as defined in claim 9, in which a combustion chamber (26)is provided between said two heater tube walls (24,25).
 11. Adouble-acting thermal gas piston engine is defined in claim 3, in whichat least one leg of said heater tubes forming said heater tube walls(24,25) is directed obliquely to the common plane of said central axesof said cylinders (1 to 6).
 12. A double-acting thermal gas pistonengine as defined in claim 2, in which the said casings (9 to 14), eachcontaining a regenerator and a cooler, are disposed so that said casingsof each row are opposite every second interval between two cylinders.13. A double-acting thermal gas piston engine as defined in claim 12, inwhich the heater tubes (32) are arranged in a heater tube wall disposedabove said cylinder row in a laterally offset combustion chamber (34).14. A double-acting thermal gas piston engine as defined in claim 13, inwhich the plane of said heater tube wall (32) is disposed obliquely withrespect to the common plane of said central axes of said cylinders (1 to6).
 15. A double-acting thermal gas piston engine as defined in claim 3,in which said heater tubes (22,30) are arranged to form at least oneheater tube wall disposed in a combustion chamber, and in whichcounter-current preheating means (29,35) is provided for heating airsupplied to support combustion from the heat of exhaust gases from saidcombustion chamber.
 16. A double-acting thermal gas piston engine asdefined in claim 15, in which said preheating means has an elongatedheat exchanger extending over substantially the full length of theengine.
 17. A double-acting thermal gas piston engine as defined inclaim 15, in which a reinforced shield (28) is provided on the floor ofsaid combustion chamber (26) for reversing the direction of flow ofcombustion gases.
 18. A double-acting thermal gas piston engine asdefined in claim 3, in which said heater tubes (22) are connected bymanifolds (20,21) respectively with said hot working space and with saidregenerator of each connecting means, and in which said manifoldsprovide a gradual change in cross section.
 19. A double-acting thermalgas piston engine as defined in claim 18, in which said manifolds extendin offset fashion from the respective cylinders and casings and that thecorresponding manifolds mutually overlap in the region of the heatertube ends.
 20. A double-acting thermal gas piston engine as defined inclaim 19, in which the two manifolds (20,21) of the same interconnectingmeans have substantially the same cross section in the neighborhood ofthe ends of the heater tubes (22).